Patent document 1 discloses a conventional penetration in which: a header ring is provided through an adaptor on an external end of a sleeve which penetrates a shielding wall of a nuclear reactor containment; a plurality of cable modules are mounted on the header ring; outside cables of the cable modules are connected with external cables through terminal parts; and inside cables of the cable modules are connected with internal cables through terminal parts. When such a penetration is in need of replacement, a welded part between the adaptor and the sleeve is cut to replace the cable modules together with the adaptor with a new one.
Since the recent nuclear power plant accident in Japan, there has been a need for enhancing safety monitoring facilities and instrumentation facilities in nuclear reactor containments. Due to an issue of radiation resistance of optical fibers, optical fibers have not been used in Japan for transmitting the measured data of temperatures and the water levels in the nuclear reactor containments.
While radiation-resistant fibers have been developed in recent years, it has been desired to develop measuring instruments, such as hydrogen detection sensors, temperature sensors, and water level sensors, corresponding to such radiation-resistant fibers and also to develop an optical fiber penetration of a partition wall of a nuclear reactor containment having pressure resistance, airtightness, heat resistance, and radiation resistance.
However, the radiation-resistant fibers as they are cannot be used as a penetration, since resin coating thereof lacks heat resistance and pressure resistance, and in addition, a fiber strand alone is easy to break and lacks durability. The radiation-resistant fibers need airtightness and durability to be used as a penetration of a shield wall of a nuclear reactor containment.